Introduction

Consumer perceptions and interest in natural cosmetics are growing as a result of the trend toward a healthy and sustainable lifestyle (Muyima et al. 2002), presenting a challenge to the industry. They need to suppress the demand for these changes while increasing efficiency and maintaining the economic viability of the process (Philippe et al. 2012; Chin et al. 2018). A more sustainable process requires advances in environmentally friendly technologies and a constant search for innovations (Álvarez-Viñas et al. 2019), both in terms of new applications and novel natural sources of bioactive ingredients (Amberg and Fogarassy 2019).

An emergent solution for a more sustainably produced natural ingredients is to obtain multiple products from the same biomass in a biorefinery process. The biorefinery is an entirely integrated and multifunctional process, which uses a variety of different raw materials and produces a range of various intermediates and finished products, enabling biomass to be used to its full potential (Laurens et al. 2017; Roux et al. 2017). This approach seeks to maximize inherent value of all components while also maximizing resource utilization (Van Hal et al. 2014; Álvarez-Viñas et al. 2019). The processes must generate the least amount of waste for the environment, lowering the environmental impact and putting less strain on ecosystem services (Zhu 2015).

The great biodiversity of seaweeds, their abundance and their biotechnological potential have aroused the interest of researchers from various fields, including the cosmetics industry (Freitas et al. 2020). Seaweeds are photosynthetic multicellular organisms with a wide range of forms, sizes, life cycles and distribution (Melo 2018; Pereira 2018). Due to their contribution to providing oxygen to the ocean and to marine food chains, they are fundamental to the environment (Chan et al. 2006; Wijesinghe and Jeon 2011). Due to their biodiversity, seaweeds have been pointed out as possible sources of new and unique active components (Paiva et al. 2018). Seaweed biomass is traditionally used in human food, while their extracts have also been widely used in organic agriculture as animal food supplements, biofertilizers and biostimulants (Wang et al. 2016; Torres et al. 2019). Some metabolites found in seaweeds are used as functional ingredients in medicine, pharmacy, and cosmetics since they have a variety of biological activities (Polat et al. 2023). The chemical characterization of seaweed extracts has revealed a wide range of molecules with distinct chemical and structural characteristics and potential biological activities (Rosa et al. 2020). Biological compounds found include phenolic compounds, sterols, small peptides, terpenes and pigments (Joshi et al. 2018; Rosa et al. 2020). Antibacterial, antifungal, antiviral, antiprotozoal, anticoagulant, antioxidant, and antituberculosis activities are some of the possible bioactivities (Guedes et al. 2011a). Compounds which may have therapeutic properties for human health due to their effects on the cardiovascular, immune, and nervous systems, with potential medical applications for tumors, allergies, oxidative stress, inflammation, thrombosis, diabetes, obesity, lipidemia, hypertension, and other degenerative diseases have also been reported (Mohamed et al. 2012; Fleurence and Levine 2016).

Seaweeds have attracted the attention of the natural cosmetics industry, and their extracts have been established in products mainly for the face and skin, as they can be used as moisturizers and stabilizers in body creams and lotions, exfoliating lotions, face masks, face washes and soaps with anti-photoaging products or after-sun skin care products (Leandro et al. 2020; Pangestuti et al. 2021). The main bioactive components of the cosmetic product are ingredients which have anti-inflammatory, antioxidant, anti-ageing, anti-irritant, regenerating and whitening properties (Mayer et al. 2009; Balboa et al. 2015; Azam et al. 2017).

In this work, three species of brown seaweeds, Bifurcaria bifurcata, Fucus spiralis and Saccorhiza polyschides, were chosen since they are very abundant along the Portuguese coast and little studied for this purpose. The main goal was to study the potential use of species in cosmetic products, as natural functional ingredients.

Material & methods

Sampling and preparation of biomass

Bifurcaria bifurcata, Fucus spiralis and Saccorhiza polyschides were collected in the intertidal in mid-summer (July 2021; water temperature of 16.2 °C; air temperature of 25.0 °C) in Viana do Castelo (41,697° N; 8,853° W). Fucus spiralis has available biomass throughout the year, showing differences in terms of seasonal features, thus in addition to the summer (S) sampling, additional harvesting in mid-autumn (November 2021; water temperature of 15.9 °C; air temperature of 16.1 °C) was performed (A sampling). The F. spiralis biomass was not fertile at the time of harvesting at both times. The seaweeds were not in the reproductive phase and were identified by experts from the group based on a guide specialized in Portuguese seaweed (Pereira 2009). The samples were washed with saltwater and any epiphytes were removed. The samples were then dried in an oven-dryer for 48 h at 60 °C (until the weight becomes stable), obtaining a visibly homogeneous biomass, milled into powder and stored in the dark until further analysis.

Nutritional composition

The nutritional potential of the seaweeds was evaluated in triplicate using the dried biomass. Protein, lipids, carbohydrates, and ash were measured using AOAC methods: Dumas’ assay for proteins was based on 990.03 AOAC; chloroform–methanol extraction method for lipids was based on 983.23 AOAC; combustion of organic matter based on 942.05 AOAC methodology for ash; and carbohydrates content was by difference (Carbohydrates = 100%–Proteins %–Lipids %–Ash %).

Biorefinery route

The successive extractions were performed in a biorefinery process (Fig. 1). In the first extraction, 250 mg of biomass (n = 8) was processed in a bead beater (Precellys Homogenizer, Bertin, USA) in three cycles with 5 mL of distilled water each (6 series of 2000 rpm for 30 s with 45 s of pause). The final 15 mL amount of extract was centrifuged at 2000 × g for 10 min. Then 7.5 mL of the supernatant was freeze-dried, yielding the Water extract (W). The other 7.5 mL produced the Polysaccharide fraction (P) by precipitation with ethanol 96% at -20 ˚C (1:3, v:v), followed by centrifugation (2000 × g for 10 min) and the pellet was dried at 60 ˚C for 24 h (Hentati et al. 2018). The second extraction was processed with the remaining biomass (pellet) resulting from the first extraction and using ethanol (99.8%) with a final volume of 15 mL. Three cycles of 5 mL of solvent were conducted using the same bead beater configuration. After centrifugation, anhydrous sodium sulfate was added to the supernatant and the solution was filtered using a PTFE filter, then dried in a rotavapor, obtaining the Ethanol extract (E). The remaining biomass (pellet) was dried at 60 ˚C for 24 h, yielding the Residue fraction (R).

Fig. 1
figure 1

Biorefinery route for seaweed biomass valorization

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Bioactive capacity

Antioxidant scavenging capacity assessment

The antioxidant capacity of each extract and fraction was ascertained via five different assays, ABTS•+ (Granados-Guzman et al. 2017), DPPH• (Brand-Williams et al. 1995), •NO (Pinho et al. 2011), O2•− (Pinho et al. 2011) and FRAP (Benzie and Strain 1996). For all the assays the extracts and fractions were resuspended in DMSO 10% (W and P) and 100% (E and R) for a concentration of 10 mg mL−1. In the four first assays, the IC values were calculated with GraphPad Prism software (version 8.4.3) through curve spline interpolation, with results presented in µg mL−1. For the FRAP assay, the results were calculated by comparing the absorbance value to a ferric sulphate standard curve and are expressed in mM Fe2+ mg−1. All the assays were performed in triplicates with a final concentration in well variating with the volume of the reaction (4–250 µg mL−1 for ABTS•+ and DPPH•, 5–333 µg mL−1 for •NO, 3–208 µg mL−1 for O2•− and 1–91 µg mL−1 for FRAP).

Enzymatic inhibition capacity of tyrosinase

Tyrosinase inhibitory activity was measured following a method of Adhikari et al. (2008) with extracts and fractions resuspended with DMSO 10% in final concentrations in a well ranging from 2 to 100 µg mL−1. The results were calculated using kojic acid positive control and IC50 values determined with GraphPad Prism software (version 8.4.3). Results are presented in µg mL−1.

Bioactive compounds

Phenolic compounds

Total soluble phenolic compounds of the extracts and fractions were measured in triplicates by the Folin-Ciocalteu method (Folin and Ciocalteu 1927), modified to microplate by Magalhães et al. (2010). The results were calculated using a gallic acid standard curve and are expressed in an equivalent percentage of extract or fraction weight (% of extract).

Total pigments

The total pigment contents (total chlorophylls (a + c) and total carotenoids) were determined following the method described by Connan (2015). The extracts and fractions were resuspended in 100% methanol and the absorbance was read. The content was calculated using the following formulae:

$$\begin{array}{l}\mathrm{Total}\;\mathrm{Chlorophylls}\;(\mathrm\mu\mathrm{g}\;\mathrm{mL}^{-1})=27.9603\ast({\mathrm A}_{632}-{\mathrm A}_{750})+12.9241\ast({\mathrm A}_{652}-{\mathrm A}_{750})+1.0015\ast({\mathrm A}_{665}-{\mathrm A}_{750})\\\mathrm{Total}\;\mathrm{Carotenoids}\;(\mathrm\mu\mathrm g\;\mathrm{mL}^{-1})=4\ast({\mathrm A}_{480}-{\mathrm A}_{750})\end{array}$$

Results are expressed in milligram of pigment per gram of extract or fraction (mg g−1).

The identification and quantification of carotenoids in biomass and E extract of F. spiralis were via high-performance liquid chromatography (HPLC). A Waters Alliance liquid chromatograph was used, which included a Model e2695XC Separation Module (gradient pump and autosampler) and a Model 2998 photodiode-array (PDA) detector (Waters, USA), operated by Empower 3 software (Waters). Samples were prepared using the acetone extract (see above in the bioactive potential section), with the addition of an internal standard (trans-β-8-apo-8′-carotenal; 170 μg mL−1). Samples were dried and resuspended in 200 μL of acetone:ethyl acetate (9:1) (Guedes et al. 2011b). A 4 × 250 mm Purospher Star RP-18e (5 μm) column (Merck) was used as the stationary phase and acetonitrile:water (9:1) served as the mobile phase. The sample was eluted for 55 min at 25 °C ± 2 °C (column heater;Waters, USA) and a flow rate of 1 mL min−1. All peaks’ spectra were recorded between the wavelengths of 250 to 750 nm. Fucoxanthin, lutein, zeaxanthin, and β-carotene (Extrasynthese) were used as chromatographic standards (HPLC grade) to compare retention periods and UV–visible spectrum. The results are given in milligram per gram of biomass and extract (mg g−1).

Statistical analysis

The data were analyzed using GraphPad Prism® V. 8.4.3. A Shapiro–Wilk test of normality was performed before the analysis of variance (ANOVA) to confirm the normal distribution of the residuals. A two-way ANOVA with Turkey’s multi-comparison test was employed to find differences between extracts or fractions and seaweeds. The significance level in all cases was 95% (p < 0.05).

Results

Nutritional composition

The dried biomass of the seaweeds was evaluated in terms of nutritional composition, specifically as quantification of proteins, lipids, carbohydrates, and ash. Results are presented in Table 1.

Table 1 Composition of seaweed biomass in terms of proteins, lipids, carbohydrates and ashes (% dry weight, average ± standard deviation, n = 3). The different lowercase letter in the same column shows statically significant differences (p < 0.05) among species
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Sacchoriza polyschides had a higher concentration of proteins, 15.84 ± 0.04% of dry weight (DW), 40% higher than F. spiralis (S or A) and 80% higher than B. bifurcata. Lipids were found in higher concentrations in F. spiralis A (8.72 ± 0.18%DW) and carbohydrates in F. spiralis S (57.89 ± 0.66%DW). In terms of ash, S. polyschides had the highest content of 41.65 ± 0.43%DW and F. spiralis A had the lowest with 23.71 ± 0.36%DW.

Extraction yields

In a biorefinery process successive extraction was used to increase efficiency, using the total biomass to obtain two different extracts and two different fractions with the lowest possible loss. The yield of each extract or fraction and seaweed is shown in Table 2.

Table 2 Yield (% biomass, average ± standard deviation, n = 8) of the successive extractions for each seaweed. Extracts: water (W), ethanol (E). Fractions: polysaccharides (P) and residues (R). The different lowercase letter in the same column shows statically significant differences (p < 0.05) among species
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The total extraction yield was between 77.40% ofDW, for F. spiralis (S) and 85.76%DW for S. polyschides. Aqueous extraction resulted in higher yields than ethanol extraction, with better results for W extract. The lowest values were obtained in the P fraction with B. bifurcata (4.62%DW) and E extract for F. spiralis S (7.30%DW).

Bioactive capacity

The bioactivity capacity of all seaweeds and extracts and fractions were assessed in antioxidant assays and tyrosinase inhibition assay (Fig. 2). In terms of antioxidant capacity, five assays were performed: ABTS•+, DPPH•, •NO, O2•− and FRAP. For the first four, the results were expressed in IC50 and IC25 and for FRAP assay the results are expressed in concentration of mM Fe2+ per mg of extract or fraction.

Fig. 2
figure 2

Results of antioxidants and tyrosine assays (average ± standard deviation, n = 3): (A) IC50 of seaweed extracts and fractions for ABTS•+ scavenging assays (µg mL−1); (B) IC50 of seaweed extracts and fractions for DPPH• scavenging assays (µg mL−1); (C) IC50 of seaweed extracts and fractions for •NO scavenging assays (µg mL−1); (D) IC25 of seaweed extracts and fractions for O2•− scavenging assays (µg mL−1); (E) FRAP Value (mM Fe2+ mg−1) of seaweed extracts and fractions; (F) IC50 of seaweed extracts and fractions for Tyrosinase inhibition (µg mL−1). Extracts: water (W), ethanol (E). Fractions: polysaccharides (P) and residues (R). The different lowercase letter shows statically significant differences (p < 0.05) among the extracts and fractions of the same species

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In the ABTS•+ scavenging assay (Fig. 2A), F. spiralis stands out with greater antioxidant capacity, especially the water extract from the autumn sampling, which had an IC50 of 62.43 ± 0.89 µg mL−1, and ethanolic extract from the summer with 144.09 ± 2.71 µg mL−1. Bifurcaria bifurcata had a better result with W extraction (188.04 ± 2.29 µg mL−1) and S. polyschides did not have enough activity to reach the value of IC50.

In the DPPH• scavenging assay (Fig. 2B), F. spiralis (A) had the best result, with no significant difference (p = 0.99) between W extract and P fractions and an average concentration of 136.44 ± 10.12 µg mL−1. This value is 1.9 times lower than that of E extract from F. spiralis (S), 261.29 ± 12.10 µg mL−1, and 2.1 times that of W extract from B. bifurcata 283.72 ± 2.38 µg mL−1. Sacchorhiza polyschides did not have enough activity to reach the value of IC50.

In •NO scavenging assay (Fig. 2C), among all the extracts and fractions, only water and polysaccharides from two species have reached the IC50. P fraction of F. spiralis (S) had the lowest activity, 115.15 ± 7.16 µg mL−1, and P fraction of B. bifurcata had the second-best concentration, 170.09 ± 15.33 µg mL−1. Sacchorhiza polyschides did not have enough activity to reach the value of IC50.

In O2•− scavenging assay (Fig. 2D) it was only possible to calculate the IC25, as none of the seaweed extracts wwere able to inhibit 50% of the radicals. The only seaweed with antioxidant capacity was F. spiralis and the extract or fraction differed depending on the season: summer P fraction had the best result with an IC25 of 98.41 ± 9.96 µg mL−1, and autumn W extract with 224.37 ± 16.37 µg mL−1.

The FRAP assay (Fig. 2E) revealed that the W extract of F. spiralis (A) outperformed the other extracts and fractions, with a FRAP value of 0.36 ± 0.01 mM Fe2+ mg−1, 3.3 times better than the ethanolic extracts of B. bifurcata and F. spiralis (S), which had no significant differences (p = 0.99). This reducing potential was not found in any of the S. polyschides extracts and fractions.

In the assay for enzymatic inhibition of tyrosinase (Fig. 2F), F. spiralis is the only species that has sufficient inhibition capacity to calculate IC50, the best extract or fraction being E from the autumn collection with a concentration of 25.08 ± 0.48 µg mL−1, 1.7 times better than water extract from the same period and 1.9 times better than E extract from summer.

Bioactive compounds

The quantified bioactive activities were related to phenolic compounds, pigments (total chlorophylls and total carotenoids)—and subsequent analysis of the carotenoid profile of the species that had the highest quantification of the same.

The results of the evaluation of total phenolic compounds are summarized in Fig. 3. Fucus spiralis (A) presented the highest percentage of phenolic compounds, 3.33 ± 0.05%E in W extract, 1.7 times better than P fraction and 1.4 times better than E extract. Sacchoriza polyschides presented the lowest value, with an average f 0.18 ± 0.04%, regardless of the extract/fraction used. Extracts W and E and P fraction of B. bifurcata and F. spiralis (S) presented intermediate values, with a small distinction for the P extract of B. bifurcata with 1.85 ± 0.08%E.

Fig. 3
figure 3

Total phenolic compounds (% Extract/Fraction, average ± standard deviation, n = 3) of each extract or fraction. Extracts: water (W), ethanol (E). Fractions: polysaccharides (P) and residues (R). The different lowercase letter shows statically significant differences (p < 0.05) among the extracts and fractions of the same species

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The total chlorophylls (a + c) and total carotenoids are shown in Fig. 4. In all species and as expected, ethanol extracts stand out for having more pigments, both total chlorophylls and carotenoids. Fucus spiralis had the most pigments, especially in the S sampling where the E extract reached 13.03 ± 0.20 mg total chlorophyll gE−1, which is 2.5 times higher than E extract from F. spiralis (A), 3.6 times higher than E extract from S. polyschides and 8.5 higher better than E extract from B. bifurcata. As for total carotenoids, F. spiralis A has 3.50 ± 0.01 mg gE−1, which is 1.3, 4.2 and 9.7 times higher than E extracts from F. spiralis (A), S. polyschides and B. bifurcata, respectively.

Fig. 4
figure 4

Total Chlorophyll (A) and total carotenoids (B) of each extract or fraction (mg g−1, average ± standard deviation, n = 3). Extracts: water (W), ethanol (E). Fractions: polysaccharides (P) and residues (R). The different lowercase letter shows statically significant differences (p < 0.05) among the extracts and fractions of the same species

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The species and extract or fraction with the highest quantification of total carotenoids were selected for characterization and results are shown in Table 3.

Table 3 Characterization and quantification of the carotenoid profile of Fucus spiralis (mg g−1, average ± standard deviation, n = 2). The different capital letters show statically significant differences (p < 0.05) for biomass and lowercase letters for E extract for each compound
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The carotenoid profile and quantification were performed for biomass and E extract of F. spiralis in both samplings, A and S, as for fucoxanthin, lutein, zeaxanthin and β-carotene. In terms of fucoxanthin, F. spiralis A showed a high concentration of this compound, 17.99 ± 0.75 mg g−1 biomass and 15.44 ± 0.27 mg g−1 in E extract, which is respectively 2.5 times and 3.0 times higher than in season S. For lutein and zeaxanthin no significant differences (p = 0.12) were found between samplings. For β-carotene F. spiralis A presented higher values than S, more specifically 3.3 times higher for biomass analyzed and 2.7 times higher for E extract.

Discussion

Multiple industries are attempting to develop more sustainable processes and explore new bioactive product sources (Yarkent et al. 2020), therefore, this study aimed to analyze the potential applications of three species of seaweeds present in the Portuguese coast. Regarding the composition of dried biomass, S. polyschides had higher concentrations of protein and ash, similar to Sánchez-Machado et al. (2004), although this results in lower values for ash. The results concerning the composition of F. spiralis are in agreement with previous studies (Paiva et al. 2014; Francisco et al. 2020) and Paiva et al. (2018) who considered the seasonal variability of the seaweed.

Seaweeds are a rich source of macro and micro nutrients such as proteins, carbohydrates, lipids, phenols, vitamins and minerals. The biomass composition and its nutritional content rely on the species and growth conditions (Trivedi et al. 2015) such as habitat, season, geographic location, and environmental factors. It is vital to investigate the whole composition of the seaweed to make better use of raw materials and natural biocompounds. This inquiry also aids in the discovery of new bioactive components.

Algal biomass is traditionally used in the feed/food sector and in agriculture. The main use of seaweeds is for direct food applications and supplementation of a specific compound, due to their nutritional value. The biomass could be used, for instance, as a source of proteins or dietary fiber from non-digestible carbohydrates (Garcia-Vaquero and Lopez-Alonso 2017; Garcia-Vaquero et al. 2017).

Besides being utilized as a whole, seaweed biomass can be fractionated in its components and consumed separately, as detailed in Cesário et al. (2018). Proteins are good as animal feed and human food additives, besides being a source of bioactive compounds and for biofunctional peptide mining (Harnedy and FitzGerald 2011). The use of carbohydrates in biotechnology, medicine, and cosmetics is possible since they provide a source of bioactive chemicals (Hayes and Tiwari 2015; Vasconcelos and Pomin 2018). Lipids are used as nutraceuticals in the food and pharmaceutical industry (Kumari et al. 2013). Lipids and carbohydrates are commonly proposed as as feedstock for biofuels (Singh and Olsen 2011). Ash is a significant source of minerals for the feed and food industries and can be used as fertilizer in agriculture (Cabrita et al. 2016; Cesário et al. 2018; Geada et al. 2021).

More than potential applications, it is important to look at the future potential of biomass. It is feasible to employ seaweeds for many purposes, resulting in differentiation and better utilization of the same biomass. Following this strategy, two successive extractions were carried out in a biorefinery process, obtaining four distinct extracts and fractions. Concerning the yield, the results showed that S. polyschides had a total yield of 85.76% DW, compared with Mzibra et al. (2018) and Hellio et al. (2002) who found higher results for extraction with S. polyschides when compared to other species, including B. bifurcata and F. spiralis. In addition, other studies (Tierney et al. 2012; Farvin and Jacobsen 2013) also showed that water extraction resulted in higher yields than other solvents, such as ethanol, as would be expected given that the seaweeds are known to have a high content of water soluble polysaccharides (Rioux et al. 2007; Gupta and Abu-Ghannam 2011).

Seaweeds generate bioactive substances that ensure their survival in habitats with a wide range of conditions and extremes (Joshi et al. 2018). The exploitation of these compounds may aid in the identification of new functional ingredients for use in the cosmetic industry.

Free radicals are a byproduct of the metabolic process of oxidation, which can start ongoing destructive chain reactions (Pinteus 2011). Oxidation can disrupt metabolism and initiate a process of oxidative stress, which can culminate in other diseases such as cancer or neurodegenerative and cardiovascular diseases (Kumar et al. 2021). Antioxidants are defence mechanisms that regulate the balance between free radicals and scavenging and have been designated as an agent that delays, prevents or eliminates oxidative damage (Cornish and Garbary 2010; Mendes 2017). In our study F. spiralis stood out by having more antioxidant activity in the assays performed. The antioxidant activities reported in this study are based in five different methods that are linked to their ability to scavenge specific kinds of radical species, some of which may be synthetic or with biologically reference. Alone, these methods usually cannot represent what truly happens in an in vivo assay or in the human body, but together, the analyses can give a better understanding of the different mechanisms of action (Munteanu and Apetrei 2021).

The findings of the ABTS•+ assay are consistent with those of previous studies. Santos et al. (2017) determined the IC50 of a B. bifurcata dichloromethane extract to be 116.25 ± 2.54 µg mL−1. Santos et al. (2020) obtained 50% of inhibition with a B. bifurcata ethanol extract at a concentration of 134.19 ± 2.12 µg mL−1, which is lower than the value found in our work. After extraction with 70% ethanol from F. spiralis collected in spring in Morocco, Grina et al. (2020) reached an IC50 with only 5.95 ± 0.6 µg mL−1, a value that is also well below that found in our work.

In our work, S. polyschides did not show DPPH• antioxidant capacity, but results were found in other studies with higher concentrations and different extraction methodologies (Bahammou et al. 2021; González-Ballesteros et al. 2021). Other studies with different species of seaweeds have shown that F. spiralis has the highest antioxidant capacity for this assay when compared to B. bifurcata and S. polyschides (Chibi et al. 2019; Grina et al. 2020, 2021) and that the A sampling has higher antioxidant capacity than the S collection (Paiva et al. 2018), which is accordant to the results presented here. Freitas et al. (2020) used an extraction process based on fractionation with F. spiralis and found the highest DPPH radical scavenging ability with the ethyl acetate fraction with the EC50 value of 38.5 µg mL−1.

In •NO assay, Andrade et al. (2013) and Lopes et al. (2012) analysed a variety of brown seaweed species including S. polyschides and although F. spiralis has the best results for this assay, they were not able to achieve the IC50. On the other hand, Soares et al. (2021) obtained IC50 with a concentration of 446.43 µg mL−1, a value higher than 333 µg mL−1 also evaluated in that study.

In our study the IC50 was not reached in O2•− assay. Lopes (2014) obtained an IC50 for F. spiralis from the coast of Peniche with a concentration of 1300 µg mL−1 and Soares et al. (2021) also obtained an IC50 of 160.04 µg mL−1 with F. vesiculosus from a Portuguese aquaculture system. The main difference in values can be due to the different methodologies of cultivation and collection, or the extraction and solvents.

Finally, in the FRAP assay, Bahammou et al. (2021) observed that the methanolic extract of B. bifurcata had a higher FRAP value (57.38 ± 2.72 mg TE g−1 DW) than four other brown seaweeds species, including S. polyschides which had a FRAP value of 25.6 ± 1.39 mg TE g−1 dry wt. Freitas et al. (2020) find values between 333.8 ± 47.1 and 2378.2 ± 93.5 µmol L−1 FeSO4 g−1 extract according to the fractionation process with F. spiralis. Related to the seasonal variation of F. spiralis, Paiva et al. (2018) found that the value is higher in winter than it is in the summer.

Interestingly, F. spiralis shows a great variation in bioactive capacity with season. Although they show a similar yield of extraction in the polysaccharides fraction (Table 1), the activity of the two fractions was extremely different and the IC50 was only reached in one of them (Fig. 2). This result also suggests that although polysaccharides are the main target of this fraction, other compounds can interfere with the activity, as shown for the phenolic compounds content (Fig. 3) and pigments (Fig. 4).

Other studies have shown the great potential of F. spiralis in terms of bioactive capacity. Noteworthy the works from Agregán et al. (2017, 2018), using F. spiralis collected in the north of Spain, which showed antioxidant capacity in water extracts from dried and fresh biomass, with best results in ABTS•+ of 1540 µg mL−1 and FRAP of 3.45 μmolTroloxEquivalent g−1 dry biomass. Agregán et al. (2018) also have compared the water extracts from fresh biomass of B. bifurcata. Interestingly in this study the results of B. bifurcata seem to be higher than F. spiralis, which might indicate that the drying of the biomass may affect the viability of B. bifurcata, compounds.

In a more extensive comparison, Obluchinskaya et al. (2022) characterised the biochemical composition of Fucus vesiculosus in Arctic locations (Irminger Sea, Norwegian Sea, Barents Sea, and White Sea). Thy found that the biochemical composition and antioxidant capacity significantly varied in the algae in different sites. The best value for the DPPH• assay was 1200 µg mL−1; the biomass in this study was dried at 20 °C and extracted with aqueous methanol (60%, v/v).

Munir et al. (2013) emphasize that antioxidants are probably the substances of greatest interest to the health and pharmaceutical industry. Pro-oxidative of reactive oxygen and nitrogen species may act in various pathogenic diseases such as cancer, cardiovascular disease, atherosclerosis, hypertension, and neurodegenerative diseases, among others (Cornish and Garbary 2010). Antioxidants operate against oxidative processes and protect these conditions.

Algal antioxidants are also included in food to prevent oxidative deterioration, lengthen food shelf life, and guarantee its safety. The use of synthetic antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tert-butylhydroxyquinone (TBHQ) is being restricted in some countries for presenting potential harm to health (Matanjun et al. 2008), while natural antioxidants, as in case of seaweeds, show a promising alternative for the industry (Baines and Seal 2012).

Moreover, extracts and fractions from seaweeds are rich in potential cosmeceutical ingredients for the cosmetic industry, such as phlorotannins, carotenoids, phenolic compounds, vitamins and minerals. They are added in cosmetics products as bioactive ingredients acting as functional ingredients in dermo treatments. Seaweed extracts can be introduced in different products, mostly in the face and skin-care products, featuring activities such as anti-cellulite, anti-wrinkling, regenerating skin cream, emollient products, anti-irritant, moisturizers and hair care (Michalak and Chojnacka 2015; Shanura Fernando et al. 2018; Gomez-Zavaglia et al. 2019). Extracts can be added to sunscreen for their antioxidant activity that protects skin from several damages such as photo-ageing, photodermatoses and skin cancer (Mercurio et al. 2015). Additionally, some cosmetics are used to improve the appearance of aged skin and may benefit from the addition of seaweed and its bioactive compounds. Some algal products as vitamin E and pigments can rejuvenate and act towards skin ageing (Keen and Hassan 2016). Nonetheless, the final concentration of extracts in the product must comply with regulatory and safety requirements, especially due to the presence of heavy metals, and allergens (e.g. terpenes) (Gellenbeck 2012). Regulatory requirements for cosmetics include the detail composition list of ingredients and stability and safety studies, for example, in vivo measurements (Pagels et al. 2022).

In the present study, seaweeds were investigated for anti-hyperpigmentation, being more effective, safe and cheap than synthetic chemical products. In the present study, F. spiralis was the only species that reached IC50, with higher activity in A sampling. Lopes (2014) obtained scavenging potential to reach IC50 with F. spiralis from the coast of Peniche with a concentration of 1300 µg mL−1 and Soares et al. (2021) also calculated the IC50 with F. vesiculosus from a Portuguese aquaculture system with a concentration of 160.04 µg mL−1.

The application of seaweed in cosmetics for combating hyperpigmentation has been described before (Sari et al. 2019). Anti-tyrosinase extracts are highly sought after for use in cosmetic products because, in addition to depigmentation activity, they also help to prevent free radical-related skin damage (Chang and Teo 2016).

Furthermore, the antioxidant capacity and anti-tyrosinase results can be partly explained by the amount of bioactive compound found in each of the extracts. However, the correlations of bioactive compounds and activity in diverse matrices such as extracts are far more complex and non-linear, and the presence of a bioactive capacity cannot be attributed to the presence of a single group of bioactive compounds. According to Foo et al. (2017) and Goiris et al. (2012), both phenolic and carotenoid content play a significant role in antioxidant and anti-tyrosinase capacity. In the case of the study, an extract containing several compounds can act in synergy and enhance its bioactive potential.

In contrast to the findings of the present study, Susano et al. (2022) found interesting results in antioxidant, anti-enzymatic, antimicrobial, anti-inflammatory and photo-protective assays with S. polyschides collected in Peniche, Portugal (about 250 km from the collecting side), although the time of collection was not specified, the main differences on biomass processing might explain the great differences. The biomass was freeze-dried, which is usually used in high-end products (e.g., microalgae), which can preserve some thermosensitive compounds and the extraction with the highest activity used ethyl acetate as a solvent, but only yielding 0.02% of the biomass.

Phenolic compounds are the seaweed's defense mechanisms in response to various stimuli. They are effective primary antioxidants because their structural rings act as electron traps, allowing them to scavenge free radicals (Kumar et al. 2021; Gomes et al. 2022). The ability to react with radicals is proportional to the number of phenolic rings present and the structure (Capitani et al. 2009). Our results are corroborated by several studies: F. spiralis showed higher concentrations of phenolic compounds compared to B. bifurcata (Grina et al. 2020, 2021) and also S. polyschides (Pinteus et al. 2017), which had low phenolic content according to Bahammou et al. (2021). Other studies (Farvin and Jacobsen 2013; Tierney et al. 2013) found high concentrations of phenolic compounds in F. spiralis compared to other species of seaweeds. Previous studies have reported a correlation between phenolic content and antioxidant capacity (Wang et al. 2009; Agregán et al. 2018; González-Ballesteros et al. 2021) and tyrosinase inhibition (Kang et al. 2004; Zengin et al. 2015; Muddathir et al. 2017; Imbs and Zvyagintseva 2018; Barbosa et al. 2020). It is essential to mention that differences in the presence of compounds are influenced by a variety of factors, including geographic location, harvesting season, climatology, and environmental conditions (Jiménez-Escrig et al. 2012).

Seaweeds also represent a rich source of natural pigments. Pigments are required for photosynthesis, and their diversity aids in acclimatization to varying light quality and intensity (Dumay and Morançais 2016). They are powerful antioxidants because they are effective free radical scavengers and can interact synergistically with other antioxidants. Furthermore, pigments are a source of other bioactivities such as anti-inflammatory, immune-modulatory, antibacterial, anticancer activity, neuroprotective and antiangiogenic properties (Pangestuti and Kim 2011; Aryee et al. 2018; Torres et al. 2019). Pigments from seaweeds are widely used as natural colouring agents (Munir et al. 2013). Although the pigment concentrations vary among the extracts and fractions studied, the total chlorophylls were higher proportions than the total carotenoids in all of them, as expected (Ryzhik et al. 2014; Fernandes et al. 2018). The characterization of carotenoids in F. spiralis showed similar results as Fernandes et al. (2018), with fucoxanthin being at least 60% of total carotenoids. Fucoxanthin is the most abundant carotenoid in brown seaweeds and because of the complex structure and substituent groups, fucoxanthin has more antioxidant capacity than other carotenoids (Wijesinghe and Jeon 2011; Kumar et al. 2021).

Carotenoids are employed in diverse areas because of their strong antioxidant, repairing, antiproliferative, anticancer and anti-inflammatory effects. They can be used in nutraceutical/cosmeceutical products to prevent oxidative stress, protect the skin by inhibiting the effects of solar UV radiation and reduce the ageing process of skin (Miyashita 2009; Berthon et al. 2017). However, the levels in the seaweeds are low, as indicated in Fig. 4.

It is worth mentioning that because synergism or antagonism reactions take place, it can be difficult to predict exactly what impact each component will have on a bio-mass or extract. Several studies show the synergistic effects of a group of antioxidants when they are combined (Foti 2007; Obluchinskaya et al. 2021). Other research has demonstrated a synergistic effect between phenolic metabolites and endogenous antioxidants (Noguer et al. 2014). Airanthi et al. (2011) also found synergy in the antioxidant activity of the combination of brown seaweed phenolics and fucoxanthin.

Conclusion

Aside from their potential, the selected species occur in abundance along the Portuguese coast, which also makes their industrial use feasible. In this study the biomass was processed in a biorefinery, obtaining two different extracts and two fractions after two successive extractions. The results obtained are promising, each one yielding better results for a different set of species and extracts or fraction. Table 4 summarizes the best extracts or fractions as well as their value for each assay.

Table 4 Summary of the best seaweed, extract or fraction and the respective value for each assay (average ± standard deviation, n = 3). Extracts: water (W), ethanol (E). Fractions: polysaccharides (P) and residues (R)
Full size table

Saccorhiza polyschides and F. spiralis presented higher results of one or more biochemical compound. The best results for the presence of bioactive compounds and the general bioactive capacity were obtained from F. spiralis extracts and fractions, with a sampling of biomass and the extract or fraction varying for each assay. Finally, it is important to remember that employing a biorefinery process and successive extraction allows for the extraction of various compounds and activities from the same algal biomass. The analysis of the residual part allows for the determination of whether even the fraction that would be discarded is useful. As a result, implementing this methodology in an industry allows for multiple applications to be obtained from a single biomass, contributing to its full utilization.